Cryopump louver extension

ABSTRACT

A standard size cryopump adapted to be mounted behind a nonstandard gate valve by extending the inlet array to a larger diameter. A standard size cryopump adapted to be mounted behind a nonstandard gate valve by using an extension attached to flanges, where the flanges correspond to the diameter of the nonstandard gate valve.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No. 61/081,461 filed on Jul. 17, 2008, the entire contents and disclosures of which is hereby incorporated by reference.

BACKGROUND

There is a growing need for cryopumps in the 500 mm to 630 mm size range for large vacuum chambers are used to produce solar cells. The large silicon arrays and thin film coatings on rolls of substrate material desorb significant quantities of water vapor as they are being processed, and also require the removal of air when they are first introduced into the chamber. One or more cryopumps are typically mounted on the vacuum chamber, each behind a gate valve that is closed when vacuum is broken to remove a batch of material, and then opened after the chamber has been evacuated to a pressure of about 0.2 Torr by a mechanical roughing pump.

Two stage Gifford-McMahon (G-M) refrigerators, which are presently being used to cool cryopumps, cool a first stage cryopanel at 50 to 100 K and a second stage cryopanel at about 15 K. The expander is usually configured as a stepped cylinder with a valve assembly at the warm end of the first stage, a first stage cold station (at 50 to 100 K) at the transition from the larger diameter first stage to the smaller diameter second stage, and a second stage cold station (at about 15 K) at the far end. A description of the operation of a G-M type refrigerator can be found in U.S. Pat. No. 3,620,029.

Cryopumps are typically manufactured with the inlet on the axis of the expander cylinder, sometimes called “in line”, or perpendicular to the axis of the cylinder, sometimes called “low profile”. Cryopumps used for pumping water vapor and air in large chambers are typically “in line” but the present concept applies equally well to both types.

Cryopumps in the size range from 500 mm to 630 mm are commonly used for large vacuum coating chambers. The cryopanels for in line cryopumps are typically axi-symetric around the cold finger. This panel design is frequently adapted to low profile cryopumps by having cutouts in the cold panel for the expander cylinder, such as in U.S. Pat. No. 5,156,007. The cryopump operates equally well in all orientations in terms of freezing gases, but during regeneration the melting cryodeposits flow out in different directions depending on the orientation and the design of the cryopump.

U.S. Pat. No. 4,150,549 describes a typical cryopump that uses a two stage G-M refrigerator to cool two axi-symetric cryopanels. The first stage cools an inlet (warm) panel that pumps Group I gases, e.g. H₂O and CO₂, and blocks a significant amount of radiation from reaching the second stage (cold) panel but allows Group II gases, e.g. Ar and N₂, and Group III gases, e.g. H₂ and He, to pass through it. The Group II gases freeze on the front side of a cup shaped cold panel and Group III gases are adsorbed in an adsorbent on the backside of the cold panel. U.S. Pat. No. 4,530,213 describes a cold panel design that consists of a series of concentric rings of increasing diameter from the inlet region to the back of the housing.

It is customary to design the cryopanels, in particular the inlet array, so that they are contained within the cryopump housing. This is the case for all of the referenced patents. It is not uncommon however for cryopanels to be mounted inside large chambers such as chambers for testing space vehicles. U.S. Pat. No. 5,819,545 provides an example of a cryopanel cooled by a G-M refrigerator that extends into a vacuum chamber. None of these are mounted behind gate valves.

SUMMARY OF THE INVENTION

The primary object of the present invention is make it easier to adapt a standard size cryopump that is mounted behind a gate valve to one with a higher pumping speed for Group I gases by extending the inlet array to a larger diameter. The larger diameter inlet array is accommodated by either increasing the diameter of the cryopump housing or having the extension of the inlet array fit into the space between the cryopump flange and the moveable gate valve plate. A secondary benefit of the latter option is a small increase in pumping speed for all gases. The extended surface is designed to accommodate a significant quantity of cryodeposit before the cryopump has to be regenerated.

The flanges that are described herein are designated as either 500 mm or 600 mm sizes in accordance with the International Standards Organization, ISO, or 22″ (22 inches) in accordance with the American Standards Association, ASA. These are referred to as standard size flanges.

In one embodiment there is provided a standard 500 mm size cryopump that can be manufactured with 22″ or 630 mm flanges with minimal changes has pumping speed increases for Group I gases proportional to increases in the inlet area, while speeds and capacity for Group II and Group III gases remain unchanged. This is accomplished by increasing the diameter of the inlet array of the cryopump. The increased diameter of the inlet array is accommodated by either increasing the diameter of the cryopump housing to match the standard inside diameter of the larger flange or adapting a larger flange to the 500 mm housing and extending the inlet array into the gap between the cryopump flange and the moveable gate valve plate. This gap is typically 2.5 to 3 cm which is sufficient to accommodate an extended array. Cryopumps with 500 mm to 630 mm flanges are used as examples to illustrate the basic concepts that can be applied to other sizes.

In a first aspect of the present invention there is provided a cryopump comprising a refrigerator having first and second stages, a cold cryopanel, a warm cryopanel, an inlet array having an extended support bracket that extends outside of the warm cryopanel, and a housing, wherein the inlet array fits inside the housing. There may be provided one or more outer louvers on a portion of the inlet array that extends outside of the warm cryopanel.

In a second aspect of the present invention there is provided a cryopump comprising a refrigerator having first and second stages, a cold cryopanel, a warm cryopanel, a housing having a close fit around the warm panel and having an first inner diameter, an inlet array that fits inside the housing, a flange that attaches the housing to a gate valve having a second inner diameter, and a bracket extension attached to the inlet array and extends the inlet array above the flange, wherein the second inner diameter is larger than the first inner diameter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of standard 500 mm cryopump panels and expander mounted behind a gate valve. A 500 mm housing, flange, and gate valve are shown on the left. A 22″ housing, flange and gate valve constructed in accordance with an embodiment of the present invention is shown on the right.

FIG. 2 is a cross sectional view of standard 500 mm cryopump panels, expander, and housing mounted behind a gate valve. A flange that adapts a 500 mm housing to a 22″ flange is shown on the right and a flange that adapts a 500 mm housing to a 630 mm flange is shown on the left, both constructed in accordance with an embodiment of the present invention. A standard 500 mm inlet louver is shown with bracket extensions that fit into the space between the cryopump warm cyropanel and the moveable gate valve plate.

FIG. 3A is a top view of a standard 500 mm cryopump inlet louver array with eight support brackets. Mounting holes for bracket extensions are shown.

FIG. 3B is a side view of FIG. 3A.

FIG. 4A is a top view of a bracket extension attached to the end of a standard 500 mm cryopump support bracket. An annular inlet collar plate is attached to the underside of the bracket extension.

FIG. 4B is a side view of FIG. 4A.

DETAILED DESCRIPTION OF THE INVENTION

In FIGS. 1 and 2, cryopump are understood to be axi-symetric as shown in FIG. 3, but for ease of comparison the cross sections of two cryopumps are shown side-by-side. The dash line separates the two cyropumps.

In embodiments of the present invention there is provided a cryopump having a housing with a larger diameter that may be attached to a nonstandard gate valve. The left half of FIG. 1 shows a 500 mm cryopump 1 a mounted behind a 500 mm gate valve 2 a. Some of the parts are common to all of the pumps that are manufactured in this series of pumps and can be adapted to different size gate valves. In the case of FIG. 1 the common or standard parts are expander 20, with first stage heat station 21 and second stage heat station 22, cold cryopanel 25, warm cryopanel 26, thermal busses 27, and bolts 15. Bolts 15 attach the inlet array 10 a, 10 b to thermal busses 27. The inlet array 10 a for the configuration on the left consists of support brackets 13 and louvers 12. In the present design there are eight support brackets and six louvers, all made of copper or a similar material. Most of the radiant heat that is incident on inlet array is conducted to first stage heat station 21 through support brackets 13 and eight copper thermal busses 27. The thermal busses 27 have constant cross sections and transport most of the heat to first stage heat station 21. Some heat is also transported to the first stage heat station 21 through copper warm panel 26. Only a small portion of 500 mm gate valve housing 8 a is shown along with moveable gate valve plate 7 a. “O” rings 9 seal cryopump flange 17 a to the outside of gate valve housing 8, and moveable plate 7 a to the inside of gate valve housing 8 a. The 500 mm cryopump 1 a mounted to a 500 mm gate valve 2 a as shown in the left half of FIG. 1 is completed by the addition of cryopump housing 18 a, and flange 17 a, which have inside diameters, IDs, of 500 mm.

The common parts of the 500 mm cryopump 1 a shown on the left of FIG. 1 can be incorporated in a 22″ cryopump 1 b and mounted to a 22″ gate valve 2 b as shown on the right of FIG. 1. The inlet array 10 b consists of extended brackets 11, louvers 12, support bracket 13 and outer louver 6. Although one outer louver 6 is shown in FIG. 1, in other embodiments of the present invention there may be one or more outer louvers. The 22″ gate valve 2 b consists of housing 8 b, moveable valve plate 7 b, and O-ring 9. Cryopump housing 18 b has an ID of 22″ as does 22″ flange 17 b. Note that the inlet array 10 b, including the extended brackets 11, is shown within the cryopump housing 18 b. Also in FIG. 1 on the right side, the radial gap between cryopump housing 18 b and warm panel 26 is larger than the radial gap on the left side, and the right side radial gap is from 0.5 to 3 cm, e.g., from 1 to 3 cm or from 2.5 to 3 cm.

In embodiments of the present invention there is provided a cryopump that may be attached to a gate valve that has a larger inner diameter than the housing of the cryopump. FIG. 2 shows a preferred way of constructing a 500 mm cryopump 1 a so that it can be more easily adapted to either a 22″ or a 630 mm gate valve 2 b, 2 c. In this design cryopump housing 18 a, and support brackets 13 with inlet louvers 12, are included in the parts that are common. A 500 mm cryopump 1 a of this design differs from the one shown on the left in FIG. 1 in having the inlet array 10 project above flanges 17 c. 17 d. In one embodiment, inlet array 10 projects less than 3 cm, e.g., less than 2.5 cm or less than 2 cm, above flanges 17 b, 17 c. In one embodiment, the inlet array is at least equal to or above the plane of flanges 17 b, 17 c. FIG. 2 shows means in accordance with the present invention of extending the common inlet array 10 to fit within a 22″ gate valve housing 8 b, as shown on the right, or a 630 mm gate valve housing 8 c, as shown on the left. The close fit, e.g., radial gap, between cryopump housing 18 a and warm panel 26 is typically 2 mm. In one embodiment, due to the close fit, there is no outer louver on the inlet array 10 as shown in FIG. 2.

For the 22″ option, annular inlet collar plate 5 b is attached to bracket extensions 4 b, e.g. by solder, which are in turn attached to support brackets 13. Cryopump flange 17 b is nonstandard in that it is a 22″ flange with an ID of 500 mm. The extended inlet array fits in the gap between cryopump flange 17 c and moveable gate valve plate 7 b. In one embodiment, this gap may be from 0.5 to 3 cm, e.g., from 1 to 3 cm or from 2.5 to 3 cm. Cryopump flanges 17 b and 17 c in FIG. 2 are up to 30% larger, e.g., up to 25% larger or up to 23% larger, than flanges 17 a and 17 b in FIG. 1.

For the 630 mm option, annular inlet collar plate 5 c is attached to bracket extensions 4 c which are in turn attached to support brackets 13. The 630 mm gate valve 2 c consists of housing 8 c, moveable valve plate 7 c, and O-ring 9. Cryopump flange 17 d is nonstandard in that it is a 630 mm flange with an ID of 500 mm. The extended inlet array fits in the gap between cryopump flange 17 d and moveable gate valve plate 7 c.

FIGS. 3A and 3B show a standard 500 mm cryopump inlet louver array 10 which consists of eight support brackets 13 and inlet louvers 12. Mounting holes 14 for bracket extensions are shown in FIG. 3B. This standard array 10 is common to all of the cryopumps shown in FIG. 2.

FIGS. 4A and 4B show details of annular inlet collar plate 5 attached to the underside of the bracket extensions 4 which are in turn attached to support brackets 13. Mounting holes 14 in supports 13 and extensions 4 provide a convenient means of attaching the bracket extensions to the support brackets is by bolting them together. In one embodiment, the bracket extensions are attached to the support brackets by spot welding or soldering.

While cryopumps with 500 mm to 630 mm flanges are used as examples to illustrate the basic concepts, these concepts can be applied to other sizes. Similarly while a GM refrigerator has been used to describe the typical cryogenic refrigerator used in a cryopump, it is also possible to use another type such as a pulse tube type refrigerator or a Stirling type refrigerator. 

1. A cryopump comprising: a refrigerator having first and second stages; a cold cryopanel; a warm cryopanel; an inlet array having an extended support bracket that extends outside of said warm cryopanel; and a housing, wherein said inlet array fits inside said housing.
 2. The cryopump as claimed in claim 1, further comprising one or more outer louvers on said extended support bracket, wherein the one or more outer louvers are on a portion of said extended support bracket that extends outside of said warm cryopanel.
 3. The cryopump as claimed in claim 1, wherein the warm cryopanel is designed to closely fit a smaller housing having a first inner diameter, and wherein said housing has a second diameter that is larger than said first inner diameter.
 4. The cryopump as claimed in claim 1, wherein the cyropump is mounted behind a gate valve having an inner diameter that matches said housing.
 5. The cryopump as claimed in claim 1, further comprising a flange that attaches said housing to a gate valve.
 6. The cryopump as claimed in claim 5, wherein the cyropump is mounted behind a gate valve having an inner diameter that matches said flange.
 7. The cryopump as claimed in claim 1, further comprising one or more inner louvers on said inlet array.
 8. A cryopump comprising: a refrigerator having first and second stages; a cold cryopanel; a warm cryopanel; a housing having a close fit around said warm panel and having an first inner diameter; an inlet array that fits inside said housing; a flange that attaches said housing to a gate valve having a second inner diameter; and a bracket extension attached to said inlet array and extends said inlet array above said flange; wherein said second inner diameter is larger than said first inner diameter.
 9. The cryopump as claimed in claim 8, wherein said inlet array extends less than 3 cm above said flange.
 10. The cryopump as claimed in claim 8, wherein said flange is up to 30% larger than a comparable flange of said housing that attaches to a comparable gate valve having an inner diameter than is similar to said first inner diameter.
 11. The cryopump as claimed in claim 8, wherein said bracket extension extends outside of said housing.
 12. The cryopump as claimed in claim 8, wherein the cyropump is mounted behind a gate valve.
 13. The cryopump as claimed in claim 8, further comprising one or more inner louvers on said inlet array. 